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Google Summer of Code Wrap up: ns-3

Friday, November 21, 2014

Today’s Google Summer of Code wrap up comes to us from Tom Henderson at ns-3, a discrete-event network simulator developed for research and educational use.

The ns-3 network simulation project creates and maintains open source software for conducting performance evaluation of computer communications networks. Widely used in networking research and development activities, ns-3 is aimed towards the academic community involved in publishing original research, as well as towards educational use in undergraduate and graduate courses on computer networking. In 2014, the project mentored four students through Google Summer of Code (GSoC).

Piotr Gawłowicz: LTE Fractional Frequency Reuse algorithms

Piotr worked on algorithms for LTE Fractional Frequency Reuse. Mobile phone systems need to use radio spectrum very efficiently, particularly in managing interference. The ns-3 project has extensive LTE modeling capability which was initiated by a GSoC 2010 project. This year, Piotr extended the ns-3 LTE module to support a relatively new strategy for balancing interference mitigation and spectral efficiency known as Fractional Frequency Reuse (FFR). In addition to the FFR model code, Piotr delivered extensive corresponding test code, documentation and examples. He even fixed some LTE module bugs, developed several additional features (such as downlink and uplink power control and per-Resource Block Radio Environment Maps), refined the model for channel quality indicators, and refactored the power and interference calculation code. Piotr's code was merged to the mainline development tree in time for the September 2014 ns-3.21 release.

Rubén Martínez: Licklider Transport Protocol

Computer networks built for operation in outer space differ significantly from those found here on Earth. The propagation and networking delays for signals sent beyond the Earth may be as long as minutes or hours, confounding traditional systems accustomed to millisecond response times. Delay-Tolerant Networking (DTN) can be applied to these types of networks, and a specific protocol known as the Licklider Transmission Protocol (LTP), similar in purpose to the popular Transmission Control Protocol (TCP) used on the Internet, is designed to reliably deliver data across these types of links.

In his GSoC project, Rubén authored a model of LTP from scratch for inclusion in our future DTN module. This model includes about 5000 lines of new code and is being tested for interoperability against other implementations of LTP by using the ns-3 emulation mode which allows the simulator to exchange data with real protocol implementations. Rubén's model will soon help open up the use of ns-3 for space data networking research.

Bufferbloat refers to a phenomenon where network performance (latency, packet jitter, throughput) is diminished due to packet buffers at the ingress of a congested link becoming too deep. New "active queue management (AQM)" approaches help minimize packet transit times in congested queues. Anh’s project focused on addressing the known problems and testing the then-unreleased ns-3 CoDel queue model originally proposed by Andrew McGregor and Dave Taht. The revised CoDel model, test scripts, and example programs were included in the recent ns-3.21 release, and variations that build on this model are planned for future releases.

Krishna Teja: Multicast IPv6 traffic support

In his GSoC project, Krishna developed the Multicast Listener Discovery Version 2 (MLDv2) functionality for IPv6 in ns-3’s Internet module. The code is completely new, closely matches Internet RFC 3810, and (when merged) will be automatically enabled for any IPv6 node. Thanks to MLDv2, each router is made aware of the multicast groups that each attached host is interested in and can dynamically reconfigure its routing table. The protocol is part of an ongoing effort to enhance the multicast routing support in ns-3 for IPv6.